Enclosed arc device



y 1937- R. F. STRICKLAND AL I 2,081,776

ENCLOSED ARC DEVICE Fil ed May 19, 1951 .Z'zxzvz zv T RS ROYAL F. 52132021: AND, HLAZRULD .ZZBLAKE ,ST'ZJAELT MDLEAN 23121-3. .A'r Tame Y.

Patented May 25, 1937 v- UNITED STATES PATENT OFFICE ENCLOSED ARC DEVICE Royal F. Strickland and Harold D. Blake, Cleveland Heights, and Stuart McLean, South Euclid, Ohio, assignors to General Electric Company, a corporation of New York v Application May 19, 1931, Serial No. 538,530

8 Claims. (Cl. 176-1) Our invention relates to are lamps of thetype posed of two portions, the middle portion and comprising refractory electrodes sealed in a bulb the end portions. In the specific form shown, of glass or similar material containing inert gas the middle portion of the filament is of afiner or vapor, and more particularly to lamps of the wire than the end portions which constitute the concentrated arc type disclosed in Strickland a'psecondary electrodes. Heretofore where other plication Serial No. 301,645, filed August 23, 192$, constructions have been employed there has been Serial No. 407,817, filed November 18, 1929, and greater liability of burn-out of the filament at its Serial No. 518,146, filed February 25, 1931, which extremities. In order to have the filament of comprise a filament in multiple with the gap beproper resistance it must necessarily be of com- 10 tween the electrodes which serves as a means for paratively small diameter wire. The result is that 10 starting the arc. The present invention is an when the are disposes itself across the filament improvement on the lamps disclosed in 'said apterminals, it is apt to burn out this fine filament. plications and resides in the construction and ar- Moreover, the greater the length of the fine filarangement of the aforesaid filament and elecment, the greater the difference between the starttrodes. ing voltage and the operating voltage of the 15 In this class of lamp when the current is turned lamp for the same length of arc gap. For these on, the filament first lights up. Inasmuch as reasons the interposition of secondary electrodes the lamp contains gas, there ensues an ionlzabetween the main electrodes and the filament tion thereof and an are forms across the filaserves to improve the performance of the lamp ment terminals. This are tends to travel to a and to increase the power factorwhich depends position across the points of greatest difference upon the relation between the starting and operof potential and therefore the arc disposes itself ating voltages. In the Strickland application across the main electrodes. Inasmuch as the re- Serial No. 518,146 is disclosed an arrangement of sistance of the filament is higher than that of the filament and electrodes in which the electrodes are gap, during the operation of the lamp, most are constituted of coiled refractory metal such 25 of the current passes across the arc gap. Acas tungsten and in which the ends of the filament cording to our invention, considered from one extend within the ends of the said electrodes. standpoint, the electrodes are formed by bend- Weprefer to embody that invention in the coning the end portions of refractory metal conducstruction of the filament and secondary electrodes tors into unclosed hooks which face each other of our lamp and preferably also to have the secand are properly spaced apart so as to provide ondary electrodes extend over and form part of an arc gap. These hooked ends are preferably the main electrodes. Various other features and bent back toward the main portion of the conadvantages of our invention will appear from the ductors so that the opposed bight portions of the following description of species thereof and from hooked, ends are closer together than the exthe accompanying drawing. 35

treme end portions of the hooks. A refractory In the drawing, Fig. 1 is an elevation of a lamp metal filament coil is disposed between the hooked embodying our invention; and Fig. 2 is an elevaportions so as to be in multiple with the arc gap, tion partially in section and on an enlarged scale and the end portions of said coiled filament surof a portion of the lamp showing more particuround the aforesaid hooked ends of the conduclarly the construction and arrangement of fila- 4O tors. Moreover, the main portion of the filament ment and electrodes. is out of line of the arc gap. In operation the S S OWH in t e draw ng. 0 3 l Comprises filament is first caused to glow and then an are a bulb l0. Inasmuch as our lamp is particularly establishes itself gradually between the leg poradapted to the production of ultra-violet radiations of the coiled filament, gradually traveling tion, the bulb I 0 is preferably composed of a 45 tothe more widely separated end portions which bore-silicate glass such as those disclosed in have the greatest difference of potential. Ulti- Strickland application Serial No. 407.817 above mately the arc establishes itself acrossthe main referred to. It is particularly desirable that the electrodes, and this is facilitated by the fact that light be approximately like sunlight. and for that these portions are slightly closer together than reason the glass of which the bulb is composed intermediate portions of the filament. should be such that it will transmit radiation The above construction provides for the prodown toabout 2900 angstroms but practically no tection of the filament, and the end portions ofradiation of the very short wave lengths. Of the filament really act as secondary electrodes. course, if the shorter wave length radiation is More specifically considered, the filament is com desired, a quartz bulb may be used, or if even 55 ferred to,

less of the ultra-violet is desired, an ordinary glass bulb may be used. The lamp is provided with the usual base H. The lead wires comprise the outer leads l2-l3 which may be 01 metal ordinarily used such as copper. The inner leads I4-I5 should preferably be of a metal of higher melting point, such as molybdenum or tungsten. Seal portions Iii-l1 are preferably of tungsten, and these are sealed in the hard glass portion of the stem I 8. United to the ends of the inner leads l4-l5, as by welding, are the tungsten conductors Iii-20. The opposite ends of these conductors are bent to constitute the main electrodes 2I-22. As shown, the ends of the conductors are hooked and the opposed bight portions are closer together than are the extreme end portions of the hooks as the ends of the hooks are bent back toward the main portions of the conductors. Extending over the electrode portions 2l-22 are tungsten coils 23-24. Those portions extending beyond the portions 2l-22 constitute secondary or intermediate electrodes and the opposite ends thereof receive the ends of the filament 25 which is of finer tungsten wire. The bulb I ll is filled with an inert gas such as argon. at a pressure of to mm. Hg and the bulb III also contains a globule of mercury 26.

In operation, as disclosed in the Strickland application, Serial No. 407,817, hereinbefore rethe electric supply circuit includes the transformer with a drooping characteristic, or a suitable ballast, so that sufficient voltage is obtained at the start to cause the filament 25 to glow. This causes an ionization of the argon and mercury vapor with the result that an arc will form across the filament terminals. This are tends to establish itself across the points of greatest difference of potential and therefore it will transfer itself immediately to a position across the secondary electrodes 23-24, and then it will transfer to a position across the main electrodes 2 l-22. As shown in the drawing, the gap between the main electrodes is made somewhat less than that between the secondary electrodes so as to insure that the are will establish itself across the main electrodes inasmuch as the difference in potential between the ends of the secondary electrodes 23-24 is not greatly different than that between the main electrodes 2l-22. The provision of the secondary electrode serves to lessen the liability to burn out of the filament 25 at its terminals, inasmuch as there is a quick transference of the are from across the said terminals. The extension of the coiled secondary electrodes over the portions 2l-22 to constitute with said portions the main electrodes serves to resist disintegration of said electrodes by the are. It will be obvious also that with the construction shown there will be less necessity for a considerable difference between the starting voltage and the operating voltage than if the filament were longer anddts terminals further apart.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric lamp comprising a bulb having therein an atmosphere of readily ionizable gas, a pair of spaced leading-in conductors sealed in a. wall of said bulb and projecting intothe interior thereof, a pair of spaced metallic main electrodes carried one by each of said leading-in wires and defining therebetween a concentrated arc gap, a filament in said bulb having its middle portion deflected away from said concentrated arc gap, and a pair of intermediate secondary electrodes of higher current carrying capacity and lower resistance than said filament each adjacent one of said main electrodes but disposed out of.the concentrated arc gap therebetween, each of said secondary electrodes being secured at one end to one end of said filament and at its opposite end being electrically connected to the adjacent leading-in conductor.

2. An electric lamp comprising a bulb having therein an atmosphere of readily ionizable gas, a pair of spaced leading-in conductors sealed in a wall of said bulb and projecting into the interior thereof, a pair of spaced metallic main electrodes carried one by each of said leading-in wires and defining therebetween a concentrated arc gap, a coiled filament of fine refractory metal wire in said bulb having its middle portion deflected away from said concentrated arc gap, and a pair of intermediate secondary electrodes of coiled coarser refractory metal wire of higher current carrying capacity and lower resistance than said filament each adjacent one of said main electrodes but disposed out of the concentrated arc gap therebetween, each of said secondary electrodes being secured at one end to one end of said filament and at its opposite end being electrically connected to the adjacent leading-in conductor.

3. An electric lamp comprising a bulb having therein an atmosphere of readily ionizable gas, a pair of spaced leading-in conductors sealed in a wall of said bulb and projecting into the interior thereof, a pair of spaced metallic main electrodes carried one by each of said leading-in wires" and defining therebetween a concentrated arc gap, a coiled filament of fine refractory metal wire in said bulb having its middle portion deflected away from said concentrated arc gap, and a pair of intermediate secondary electrodes of coiled coarser refractory metal wire of higher current carrying capacity and lower resistance than said filament each adjacent one of said main electrodes but disposed out of the concentrated arc gap therebetween, each of said secondary electrodes being secured at one end to one end of said filament and at its opposite end being electrically connected to the adjacent leading-in conductor, and end portions of said secondary electrode coils constituting portions of said main electrodes.

4. An electric lamp comprising a bulb having therein an atmosphere of readily ionizable gas, a pair of spaced leading-in conductors sealed in a wall of said bulb and projecting into the interior thereof, a pair of spaced metallic main electrodes carried one by eachof said leading-in wires, and a coiled refractory wire filament inside said bulb connected as a shunt across said electrodes and having its middle portion deflected away from the gapbetween said main electrodes, said filament having one end electrically connected to each of said leading-in conductors adjacent said electrodes but out of the arc gap therebetween, the said end portions of said filament being of higher current carrying capacity and lower resistance than the intermediate portion.

5. An electric lamp comprising a bulb having therein an atmosphere of readily ionizable gas, a

wall of said bulb and projecting into the interior thereof, a pair of spaced metallic main electrodes 75 carried one by each of said leading-in wires, and a coiled refractory wire filament inside said bulb connected as a shunt across said electrodes and having its middle portion deflected away from the gap between said main electrodes, said filament having one end electrically connected to each of said leading-in conductors adjacent said electrodes but out of the arc gap therebetween, the said end portions of said filament being of coarser wire of higher current carrying capacity and lower resistance than the intermediate portion.

6. An electric lamp comprising a bulb having therein a readily ionizable gas,'a pair of spaced leading-in conductors sealed in a wall of said bulb and projecting into the interior thereof and having unciosed hooked ends raced toward each other and spaced apart to form an arc gap, the end of each of said hooks being bent back toward the main portion of the conductor from which it is formed so that the opposed blght portions are closer together than the extreme end portions of said hooks, a coiled refractory wire filament in said bulb having its middle portion deflected away from said are gap, and a pair of intermedi; ate secondary electrodes of higher current carrying capacity and lower resistance than said filament each adjacent one of said hooked ends but disposed out of the arc gap therebetween, and each of said secondary electrodes being secured at one end to one end of said filament and at its opposite end to the end of the adjacent hook.

7. An electric lamp comprising a bulb havin therein a readily ionizable gas, a pair of spaced leading-in conductors seal in a wall of said bulb and projecting into the interior thereof and having unciosed hooked ends raced toward each other and spaced apart to form an arc gap, the end of each of said hooks being bent back toward the main portion or the conductor from which it is formed so that the opposed bight portions are closer together than the extreme end portions of said hooks, and a coiled refractory wire filament in said bulb connectedas a shunt across said are gap and having its middle portion deflected away from said are gap, the end portions of said filament being of higher current carrying capacity and lower resistance than the intermediate portion and being secured at each extremity to the end of one of said hooks.

8. An electric lamp comprising a bulb having therein a readily ionizable gas, a pair of spaced leading-in conductors sealed in a wall of said bulb and projecting into the interior thereof and having unciosed hooked ends faced toward each other and spaced apart to form an arc gap, the end of each of said hooks being bent back toward the main portion of the conductor from which it is formed so that the opposed blght portions are closer-together than the extreme end portions of said hooks, and a coiled refractory wire filament in said bulb connected as a shunt across said are gap and having its middle portion deflected away from said are gap, the end portions of said filament being of coarser wire of higher current carrying' capacity and lower resistance than the intermediate portion, and the said coarser wire end portions each being closely coiled around one of said hooks and extending beyond the end thereof out of the line or the arc gap.

ROYAL F. STRICKLAND. HAROLD D. BLAKE. STUART MCLEAN. 

